1. Field of the Invention
The present invention relates to a navigation system. More particularly, the present invention relates to a system and a method for providing a navigation service inside of a building by using visible light communications.
2. Description of the Related Art
Recently, the luminous efficiency of Light Emitting Diodes (LEDs) has been improved while the unit price of LEDs has dropped. Accordingly, LEDs are more commonly used not only in the special illumination market, such as for handheld devices, displays, automobiles, traffic lights, advertising boards and the like, but also in the general illumination market, such as fluorescent lamps, incandescent electric lamps and the like. Also, interest in optical wireless technology that is complementary with Radio Frequency (RF) technology has currently been increased because of the limitations of RF technologies. That is, with an exhaustion of frequencies in the RF band, a possibility of an error among wireless communications, an increase of the security requirements for wireless communications, the advent of the very high speed ubiquitous communication environment of fourth generation mobile communication (4G) wireless technology, etc., studies are being performed on visible light wireless communications using visible light LEDs by many enterprises, research institutes, etc.
The visible light communication technologies that deliver information by using visible light are safe, and have a widely available band. Also, they can be used without being subject to regulation, and have advantages in that the reception range of information communicated using the visible light technologies can be accurately detected. That is, an area where the visible light reaches or a direction in which the visible light moves can be easily seen without the need for complicated and expensive equipment. Accordingly, the visible light communication technologies have reliability which makes them more secure, and also have advantages such as the ability to be driven with low electric power thus reducing their power consumption in comparison with other technologies. Accordingly, the visible light communications can be applied in such diverse locations as a hospital, an airplane, etc., where the use of RF is limited and a value-added information service can also be provided by using an electric light board. A description will now be made of these visible light communications with reference to the drawings.
FIGS. 1A and 1B are views illustrating configurations of communication systems using conventional Visible Light Communications (VLC). FIG. 1A is a view illustrating a conventional VLC system. The conventional VLC system is configured to include lamps 101, 102 and 103, which comprise Light Emitting Diodes (LEDs) or Laser Diodes (LDs). Lamps 101, 102 and 103 perform data transmission/reception (Tx/Rx) by using visible light while simultaneously performing the role of ambient lighting. Communication devices 120 and 121, each of which is equipped with a visible light Tx/Rx module, are able to perform data Tx/Rx with the lamps. As illustrated in FIG. 1A, the communication devices may include a mobile terminal 120 such as a mobile phone, a Personal Digital Assistant (PDA) and the like, and a fixed type terminal 121 such as a desktop and the like.
FIG. 1B is a view illustrating a peripheral interface system using VLC. Communications among peripheral devices using VLC includes a communication system which performs, by using visible light, communications among a communication device 130 such as a notebook computer, a desktop computer, etc., each of which is equipped with a visible light Tx/Rx module, a mobile device 131 (e.g., a mobile phone, a PDA, etc.), a peripheral device 132 (e.g., a printer, etc.), and a small-sized digital device (e.g., a digital camera, an mp3 player, etc.). The peripheral interface using VLC has advantages in that it is secure and can be implemented so as to be driven with low electric power.
In addition, the VLC can be utilized efficiently in connection with a communication system using a different communication media, such as a wire or wireless communication media. As an example, a detailed description will be made below of a VLC system that provides information by using lighting inside of a building in connection with power line-based Power Line Communications (PLC).
FIGS. 2A and 2B are views illustrating conventional configurations of communication systems using conventional PLC and VLC. FIG. 2A illustrates a system that broadcasts music information using a communication system employing PLC and VLC. With reference to FIG. 2A, a communication system includes a music server 201 in which data to be provided to users is stored, a power line 202 for performing PLC between the music server 201 and a lamp 203, the lamp 203 which performs PLC to receive data from the music server 201 and then transmits the received data as a visible light signal, and a mobile terminal 131 for receiving the visible light signal transmitted from the lamp 203. In the communication system employing PLC and VLC with as illustrated in FIG. 2A, data is transferred from the music server 201 to the lamp 203 through the PLC based on the power line 202. The lamp 203 modulates the received data into a visible light signal, and then broadcasts the visible light signal by using an LED. On receiving the visible light signal transmitted from the lamp 203, the mobile terminal 131 converts the received visible light signal into an electrical signal. The mobile terminal 131 can then use the electrical signal to perform a function, such as playing a music file. FIG. 2B illustrates a system for broadcasting image information to users by using a communication system including PLC and VLC. The system depicted in FIG. 2B has substantially the same configuration and performs substantially the same operation as the configuration and operation of the system illustrated in FIG. 2A. More specifically, the communication system of FIG. 2B includes a movie server 205, a power line 206 and a lamp 207. The movie server 205 provides information to lamp 207 through power line 206. The lamp 207 receives and modulates the information so that it can be broadcast using visible light to a terminal 208. The terminal 208 can then use the information to view a movie and the like. Accordingly, in the VLC system, information originating from the movie server 205 can be provided to a terminal by using VLC wherever lighting is illuminated.
A mobile communication terminal, such as a mobile phone, a Personal Communications Services (PCS), an International Mobile Telecommunication-2000 (IMT-2000), a PDA and the like which a user can carry with him/her, provides a simple voice call function for a user. Recently, various types of convenience functions, such as a message Tx/Rx function, a wireless internet function, a schedule management function, a navigation function, etc., besides a simple voice call function, have been added to the mobile communication terminal.
One of these convenience functions is a navigation function which uses a Global Positioning System (GPS). Using this function, a user is provided with path information which leads from the user's current location to an input destination. The user is thereby provided with an optimal path and a movement direction by which to arrive at the input destination. Generally, such a navigation system can determine the optimal path through map data stored in a database.
This type of navigation system has been primarily developed for use in navigating a car. However, further developments are being made for a navigation device in the form of a mobile communication terminal, such as a mobile phone, etc., for use by a pedestrian who pays a visit to a destination in a crowded downtown or in an unfamiliar place. The navigation device for a pedestrian enables the pedestrian who carries the navigation device with him/her to be supplied with an optimal path and to monitor the navigation device for a movement direction.
However, in the case of the navigation system employing the prior GPS, a problem is raised in that, if a pedestrian enters the inside of a building or travels underground, he/she cannot receive a GPS signal, and can then not use the navigation service.
Accordingly, in response to the increasing trend of large buildings, such as skyscrapers, large shopping malls, large underground shopping centers, etc., in which a GPS navigation signal is not present, there is an increasing need for navigation inside of a building.